Molecular analysis of mitochondrial DNA from rye (Secale cereale L.)

Molecular characterization of mitochondrial (mt) DNA of rye (Secale cereale L.), free of significant amounts of contaminating chloroplast (cp) DNA, was initiated using the open-pollinated cultivar 'Halo' as a source of mtDNA. Based on the compilation of data from restriction patterns, the molecular size of the mtDNA was estimated to be 410 Kb and its buoyant density was determined as 1.705 g/ml. Southern hybridization, using labelled cp genes (P700 and ribulosebiphosphate-carboxylase large subunit), indicated the presence of cpDNA-homologous regions on putative mtDNA fragments. Mt DNAs of inbred lines with fertile and cytoplasmic male sterile (CMS) 'Pampa' cytoplasm were also analysed. Whereas the restriction patterns of mtDNAs of 'Halors and the fertile line turned out to be identical, 'Pampa' mtDNA showed a unique restriction pattern, indicating (as in most other CMS systems) the involvement of mtDNA rearrangements in the expression of male sterility in rye. All 3 mtDNAs investigated contain regions homologous to the plasmid S1 of the CMS-S cytoplasm of Maize (Zea mays), as indicated by hybridization experiments. In 'Pampa' cytoplasm the S-homologous sequence is located within a rearranged region of mtDNA.